This invention is concerned with coding related sorting systems, methods and apparatus particularly useful in the agricultural industry. The sorting of agricultural commodities during or shortly following the time of their harvest has assumed increasing importance as an aspect in achieving both production economies and higher quality processing and packaging prior to the introduction of the commodities into the consumer market. Concerning the utilization of coding and sorting systems in conjunction with harvesting, the development of economical and efficient field sorting techniques for several agricultural commodities would be of considerable value to the industry. As one example, potatoes, by virtue of the soil conditions extant in the regions of their cultivation, are removed from the ground in conjunction with rocks, clods and the like which ultimately must be separated from the harvested material bulk. Where such removal or sorting procedures are carried out at processing or collection stations removed from the locale of the producing fields, higher expenditures are necessitated for hauling the greater weight in bulk of the harvest. Conversely, where rock materials and the like can be removed at the site of the harvest, disposal problems associated with the waste are minimized and the cost of transporting the harvested product to collection regions or stations is considerably lower. Commercially grown onions represent another of such commodities, which when harvested, necessarily are collected with dirt clods and the like often representing 50% of the bulk of the harvested material. Where such bulk is transported to receiving stations prior to segregation of the commodity from the waste, a considerable expenditure for transportation and the like is incurred. By separating the dirt clods early or in conjunction with the harvesting procedure itself, convenience and economy readily are recognized.
Perhaps one of the more complex harvesting techniques is associated with the tomato. Currently, about 300,000 acres in California and a smaller but significant number in the midwest are devoted to the production of processing tomatoes. Substantially all of the California acreage is machine harvested, while about 10% of the acreage in the midwestern locale is so harvested. Presently grown tomato cultivars ripen non-uniformly and, as a consequence, they either must be harvested by hand as they ripen, or, if practical, once-over mechanical harvesters are employed, the tomatoes all being harvested at one time and the resultant harvest providing a bulk quantity thereof which must subsequently be sorted to remove green or immature fruit. Particularly in consequence of labor related economic factors, the industry has looked with favor toward harvesting procedures of the once-over variety wherein the vines are uprooted, all tomatoes removed therefrom and transported to collection stations for packing house processing. Where field sorting of the tomatoes in accordance with their degree of ripeness is provided, such provision generally is made through the utilization in the field of about ten to twenty-five laborers who ride upon the harvester to carry out visual coding and sorting. The consequent labor expense as well as the significant increase in machine size and weight have been found to impose severe limitations on the effectiveness of the mechanical harvesting system. Size and weight are particularly complicating factors where the harvesters are utilized in wet or soggy fields, an environmental condition very often encountered in the midwestern regions. For a more detailed discussion of the latter problems, reference is made to the following publication:
I. harbage, R. P., T. H. Short, and Dale W. Kretchman, (1972). Considerations for Mechanizing Processing Tomato Production in Ohio. Agricultural Engineering Series 12, Ohio Agricultural Research and Development Center, Wooster, Ohio. PA1 Ii. stephenson, K. Q. (1974). Color Sorting System for Tomatoes. Transactions of ASAE, 55: 1185. PA1 Iii. johnson, Paul E. (1973). Tomato Harvesters for the Midwest. Unpublished paper. Agricultural Extension Service, Purdue University. PA1 Iv. wright, Paul L. (1972). The Latest on Machine Harvesting of Processing Tomatoes in Ohio. Unpublished paper, Agricultural Extension Service, Fremont, Ohio. PA1 V. kattan, A. A., R. H. Benedict, G. A. Albritton, H. F. Osborne, and C. Q. Sharp. (1968). Mass Grading Machine-Harvested Tomatoes. Arkansas Farm Research, Vol. XVIII, No. 1, January-February, 1968, p. 5. PA1 Vi. kattan, A. A., C. Q. Sharp, and J. R. Morris. (1969). A Mechanical Sorter for Tomatoes. Arkansas Farm Research, Vol. XVIII, No. 1, p. 8, January-February, 1969.* FNT *See also: Gould, W. A. "Mass Sorting of Mechanically Harvested Tomatoes." Research Circular 209, December, 1975. Ohio Agricultural Research and Development Center, Wooster, Ohio. PA1 Vii. heron, J. R. and G. L. Zachariah. (1974) Automatic Sorting of Processing Tomatoes. Transactions of ASAE, 55:987. PA1 Viii. stephenson, K. Q. (1964). Selective Fruit Separation for Mechanical Tomato Harvester. Agricultural Engineering, 45:250-253, May, 1964. PA1 Ix. stephenson, K. Q. (1966). Automatic Sorting System for Tomato Harvesters. Procedures of National Conference on Mechanization of Tomato Production, Purdue University, Lafayette, Indiana. 1966. PA1 X. hamann, Donald D. and Daniel E. Carroll. (1971). Ripeness Sorting of Muscadine Grapes by Use of Low-Frequency Vibrational Energy. Journal of Food Science, 36: 1049. PA1 Xi. hamann, D. D., L. J. Kushman, and W. E. Ballinger. (1973). Sorting Blueberries for Quality by Vibration. Journal of the American Society for Horticultural Science, Vol. 98, No. 6, p. 572-576, Nov., 1973. PA1 Xii. stephenson, K. Q., R. K. Byler, and M. A. Wittman. (1973). Vibrational Response Properties as Sorting Criteria for Tomatoes. Transactions Of ASAE, 16:258, March, 1973.
Where the extent of acreage involved in a given harvesting region is sufficiently large, more expensive machinery incorporating complete sorting systems becomes more practical, however, particularly in midwestern regions and the like, such cost considerations generally have precluded the utilization of harvesting systems incorporating automatic sorting devices. However, the need remains for a practical embodiment of a harvester mounted sorting system inasmuch as typical tomato cultivars do not ripen uniformly. Consequently, once-over harvesting procedures necessitate the collection of tomatoes of a broad variety of maturities including immature fruits, the value of which is considered dismissable. This situation is particularly prevalent in the midwest where mechanical harvesting commences when about 30% or more of the fruit is green or immature. Additionally, rainfall during harvesting periods is generally found to be higher in the midwest than in other regions, thus creating wet ground conditions which, as noted above hinder movement of the harvesters in the field. This climate also asserts greater variation in the maturity range of a harvested crop. Further information concerning such harvesting aspects may be found in Publication I and the following publication:
Several varieties of tomato harvesters are currently produced, the capacity for more current models being in the range of about thirty tons of fruit per hour. Where manual sorting is incorporated with the machine, such capacities are considerably limited. Human sorting has been found to average about one-half ton per hour on a per capita designated basis. As is apparent, some other form of sorting is required to improve sorting capacities. For further discussion concerning the above harvesting considerations, reference is made to Publication I and the following publications:
In view of the significant quantity of machine picked tomatoes which are immature or green, and which have no significantly discernable value, a considerable advantage would accrue with the utilization of an economic field harvesting scheme automatically disposing of such tomatoes in the field site for natural biodegradation. Without such sorting, all harvested tomatoes are required to be hauled to the processing plant for sorting purposes, a requirement which levies higher costs upon the harvesting procedure.
Looking now to in plant sorting techniques, typical sorting systems involve a non-destructive coding followed by a segregation technique sometimes referred to as "switching". While most industrial sorting procedures for comestibles are carried out by labor utilizing both the visual as well as tactile senses, investigations have been conducted into techniques for reducing the labor intensity of such procedures. For example, with respect to tomatoes, the specific gravity thereof has been found to increase with ripeness and has been suggested as a sorting technique. In one such arrangement, a gravity sorting system is provided wherein tomatoes are floated in solutions of ethanol and water. Typically 80 to 90 percent of the green tomatoes and 15 to 25 percent of lower quality acceptable tomatoes will float. In another such arrangement, a low percentage brine solution has been utilized in an arrangement wherein the rate of upward floatation movement of tomatoes served as the coding procedure. For further information concerning such coding and sorting techniques reference is made to the following publications:
Sorting concepts for tomatoes based upon the light reflectance properties thereof have been proposed or developed as apparatus, for instance, electronic color sorters wherein light reflecting from the fruit is sensed by a photoresponsive device. Utilizing appropriate coding or selecting circuitry, a form of switching then is incorporated with the sorting system such as an air blast or plunger providing an ejection function. These systems are available only at such relatively higher costs as are considered above the level of practicality for plant or field installations of smaller extent. For field harvesting adaptation, the electronic or light reflectance systems are called upon to operate under somewhat rigorous and dirty field conditions. Accordingly, maintenance costs of considerable extent necessarily are encountered in addition to a relatively high initial capital investment. Further elaboration upon this form of sorting for tomatoes is provided, for example, in Publication II and in the following publications:
Investigations also have been conducted into the response of tomatoes and other fruits to vibrational phenomena. For example, a downwardly inclined trough mechanically excited by an electrodynamic shaker utilized for the purpose of separating grapes into ripeness categories has been described in U.S. Pat. No. 3,680,694 as well as in the following publication:
This same approach has been used in similar attempts to sort blueberries as described in the following publication:
The above studies generally recognize that vibrational sorting is based upon differences in resiliency of the object subjected to such vibration and that correlations are available between fruit or vegetable ripeness and this exhibited resiliency. The response of tomatoes to vibration as a potential criterion for sorting has been studied. For instance, the resonant frequencies of tomatoes of various maturities has been investigated, the response of a green tomato so excited being found to be approximately six times that of a ripe tomato. A more detailed discourse concerning this subject is provided in the following publication:
To the present time, sorters operating upon vibrational principles have been found to be somewhat impractical, their capacities for field harvesting applications being considered too low for the volumes of sorting usually required, and the mechanisms generating required vibration being both expensive and difficult to use at requisite frequencies.